Based on a quick research on EU 92/21 weight standards has been in effect since 1992. So I might question the actual weight of the 190 back in 1986 or just reduced the weight added for post EU 92/21 cars. Which is 68g driver, 90% fuel, and 7kg luggage.

The biggest drawback for the C-AMG with any motor is weight. The 3280 lbs of the coupe minus EU 92/21 is right at 3020+ lbs without fuel, person or luggage. And you know what weight does to a car on the road course or auto cross. It can be less costly to add power than it is to reduce weight.